In order to recycle paper, there is a method of forming an image on the paper with decolorable toner. The decolorable toner generates color in image forming process, and is erased when the toner is heated and the color material in the toner loses its color. If the printing which is not required to be recorded permanently is carried out on paper with the decolorable toner, the paper subjected to printing processing, reading processing and then color erasing processing can be reused, which can save paper resource.
Generally, the development (printing) based on the decolorable toner is carried out with ink of a color (for example, blue) different from black color, so as to distinguish the development from the printing based on non-decolorable toner. However, as printing object is generally printed with black color, the document printed with blue color and the like may cause a sense of discomfort (for example, hard to read) to a reader.
However, if the printing based on the decolorable toner is carried out using black toner, it is difficult to distinguish the printing based on the decolorable toner from the printing based on the non-decolorable toner in a case of a color printing as well as a case of a monochrome printing.
Thus, the present invention provides an image forming apparatus which can easily identify whether the printing is carried out with non-decolorable toner or decolorable toner.